Electrical Relay Question

[CobyRupert]

How many Watts (or amps) of lights is the relay switching? To many amps will fuse (together) relay contacts.

When you say fail, does this mean no longer turns lights on, or allows current to lights (glow) when it should be off?

Your initial post, described "leakage" across the relay contacts. It may be LED lights draw so little current, that a little leakage causes glow, whereas normally (with incandescent lights) there wouldn't be enough to notice this.

Check that your alternator/system voltagewhen running is somewhere around 13.8-14.2 VDC and not something larger causing this leakage, or fusing.

Recently, my 4 wheeler kept going through ignition switches, 1 or 2 a year. I kept thinking it was the cheap aftermarket ones I'd replace the previous with. The switches weren't the problem, just the symptom. I finally figured out the cause was a bad voltage regulator, the switch was designed to interrupt 12-14 VDC, not the 18-20+ VDC I had when running.

 

[SPYDERLK]

Second one has failed. Not sure why. What things can lead to failure? Can I take it apart for clues to prevent a third failure? Have the new one in hand but want to avoid replacing a third time.

If you are using LED lights the current is probably just a few amps. Virtually any switch will handle this fine and there will be those made with contacts and action designed for 12V service. Low voltage service such as this requires a wiping contact to stay clean for good reliable contact. ... It is unlikely that the relays you are getting have such contact design. And since relays are not needed for the low amp anyway you are subject to a double whammy.

 

[k0ua]

As stated we need to know the failure mode. For instance an open coil would be entirely different than burned contacts. You must know the failure mode, by inspection and testing. Easy for me to say with 50 years of electronics experience. I could make guesses by remote control but to know what happened to the relay and to make actual useful recommendations would require hands on inspection and testing.

As an example a novice troubleshoot will look at a "blown" fuse and gain no knowledge at to WHY the fuse ruptured. An experienced troubleshooter will do a thorough examination of a fuse, and will likely come up with a hypothosis of the probable failure mode of the fuse. It could be vibration failure, a slight or near normal current load that caused overheating and the fuse to "sag" or it could be violent and catastrophic overload that cause vaporisation of the fuse link.

This would lead the expert troubleshooter in different directions as to a resolution of the problem. It is all about having experience. You gain that experience through years of solving these types of problems. Then once all of that experience is gained, you get old and die.

 

[CobyRupert]

It is all about having experience. You gain that experience through years of solving these types of problems. Then once all of that experience is gained, you get old and die.

Exactly. You learn more and more about the details of the specific item. Or said another way: You learn more and more about less and less until you know absolutely everything about nothing!

 

[LD1]

Second one has failed. Not sure why. What things can lead to failure? Can I take it apart for clues to prevent a third failure? Have the new one in hand but want to avoid replacing a third time.

Ditto what others have said....need to know "how" it failed before anyone can even take a guess as to "why".

IF it failed the same way as last time.....leaving the lights on, but dim.....perhaps it isnt an issue with the relay at all. Maybe its the wiring.

Posts 85 and 86 on the relay are the "control". Those posts energize the coil. One is grounded, one gets 12v......when that happens.....87 and 30 "close" and you have power to the lights.

IF you have an issue with 85 and 86.....something causing voltage to be induced into whichever of those you have as hot......could cause an issue. But not a full 12v being induced. IF something is shorted elsewhere and inducing ~4-5v into the control side.....it could cause the contacts to close, but make a weak connection and result in dim lights that wont shut off.

How is the switch wired to the relay? are you switching the ground side and having 12v present at all times at the relay? or is ground present at all times and you are switching the 12v for the control?

What are you using for a switch? Whats the amp rating? And whats the amp rating of the lights? Possible to just forget the relay and wire lights direct to switch?

 

[Luke'sScreenName]

Not exactly relevant but I just love this graph (and am not unknown atop Mount Stupid)

 

[k0ua]

View attachment 480043

Not exactly relevant but I just love this graph (and am not unknown atop Mount Stupid)

THAT is an interesting graph. And likely very true.

 

[k0ua]

And just to throw more confusion and doubt into the mix, not all Original Equipment Manufacture's (OEM) engineers are competent. Just because you hold an electrical engineering degree that doesn't mean that you have a feel for real world applications.

Many long tenured technicians have a "whole lot more smarts" than some engineers. Circuits can be designed with minimum specifications or substitutions can be made during production that run too close to the edge of design spec's that can cause problems in the actual field application.

Long story short, the "thing" could be designed wrong from the get-go and never work reliably, and require total redesign or some sort of field expedient work around. Don't think I haven't fixed many engineers mistakes in my career first as a technician and later as an engineer myself.

If it has **** or wheels you are going to have trouble with it.

 

[tcartwri]

View attachment 480043

Not exactly relevant but I just love this graph (and am not unknown atop Mount Stupid)

Excellent.

 

[tcartwri]

To the OP, the supply wire may be of insufficient gauge.